US Energy Secretary Ernest Moniz speaks during a press conference at the 2016 Nuclear Security Summit in Washington, DC, April 1, 2016.

U.S. Energy Secretary Ernest Moniz on Thursday said Russia is forcing the United States to focus more intently on its nuclear security, and he added that the U.S. should work to modernize its nuclear deterrent.

"I mentioned earlier Russia and stimulating some additional thinking on energy security. They've also stimulated some additional thinking on nuclear security issues unfortunately," Moniz said during a speech at Columbia University on Thursday evening hosted by the Center on Global Energy Policy.

The U.S. Energy Department's National Nuclear Security Administration is tasked with guarding the safety and integrity of the nation's nuclear arsenal.

Moniz said he believes President Barack Obama has the right vision of working toward a nuclear weapon-free world, but he said the next administration will face difficult choices because "there is no reason today to think that that is not going to be a multi-decade activity."

"So a lot of money is going to have to be spent on modernizing the nuclear deterrent and rethinking exactly how it's used," he said, without elaborating on what form those changes should take.

Moniz added that Russia's annexation of Crimea and ongoing incursions into Ukraine since 2014 made the United States and Europe reconsider civilian energy policy, because the European Union is heavily reliant on imports of Russian natural gas.

Moniz did not refer to specific actions Moscow has taken to stoke U.S. thinking on nuclear security, but the Kremlin has taken a number of steps recently that have concerned the White House.

Earlier this month, Russia suspended a pact with the United States to reduce the amount of surplus weapons-grade plutonium still held by both countries.

The same week, Russia positioned missiles that are capable of carrying nuclear payloads into an area bordering Poland and Lithuania, both NATO members. The Russian Defense Ministry said the activity was part of routine drills.

An ultra-nationalist ally of Russian President Vladimir Putin this week said America risked being dragged into nuclear war if Hillary Clinton becomes president, though the lawmaker is widely considered something of a political clown, and members of the U.S. intelligence community has said that Russia wants to influence the presidential election in favor of Republican candidate Donald Trump.

The United States and the European Union have imposed sanctions on a number of Russian individuals and taken measures to handicap the country's defense, banking, and energy sectors, alleging Moscow violated Ukraine's sovereignty and territorial integrity.

Iran deal 'wasn't to solve all the problems'

Moniz also addressed criticisms of the Iran nuclear agreement he helped hammer out last year.

The deal, agreed to by Iran and six other nations, lifted some sanctions on the long-time U.S. adversary. In exchange, Iran accepted limits on its atomic energy program and allowed inspections of its nuclear facilities to resume.

Critics claim the deal did not address a host of issues, such as Iran's support for the Lebanese militant group Hezbollah, which the United States considers a terrorist organization.

Moniz said the negotiations were meant only to address the immediate threat of Iran's nuclear program and noted U.S. sanctions on Iran remain in place over its human rights record and support for U.S.-designated terrorist groups.

"Just as when Reagan negotiated arms control in the 80s, it wasn't to solve all the problems we had with the Soviet Union," like the former union's role in fueling proxy wars and restrictions on Jewish emigration, Moniz said.